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Hastelloy & Monel Machining Services

 HASTELLOY & MONEL MACHINING SERVICES 

CNC Hastelloy and Monel Machining for Corrosive Environments 

Hastelloy and Monel are what engineers specify when nothing else survives the environment reducing acids, chlorides, seawater, flue gas. They are also, in the case of the Hastelloy C grades, among the most difficult materials in common industrial use to machine: the worst combination of work hardening and gumminess you will encounter outside of a research lab. 

Steelcrest Precision machines Hastelloy C-22, C-276 and B-2, and Monel 400 and K-500. We are ISO 9001 certified and machine to AS9100-compliant processes as we pursue full AS9100 certification. Turning holds ±0.0005", precision turning ±0.0002", and wire EDM ±0.0002" to ±0.0005", which on the Hastelloy grades is frequently the economic answer rather than the technical fallback. 

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Alloys We Run

Alloy Type Where it earns its place
Hastelloy C-276 Ni-Mo-Cr The general-purpose severe-corrosion alloy. Chemical processing, pollution control, flue-gas desulfurisation.
Hastelloy C-22 Ni-Mo-Cr Broader corrosion resistance than C-276 across oxidising and reducing conditions.
Hastelloy B-2 Ni-Mo, no chromium Reducing acids, principally hydrochloric. Not for oxidising service.
Monel 400 Ni-Cu, solid solution Marine hardware, valve trim, seawater service. Gummy but distinctly easier than the Hastelloys.
Monel K-500 Ni-Cu, age hardenable to HRC 27–35 Marine shafting, pump and valve components, non-sparking tooling. Notorious for galling.

Tolerances and Surface Finishes We Hold 

Our machine capability applies, but achieving it on these alloys is slow and tool-wear driven rather than difficult in principle. On Monel K-500 aged to HRC 27–35, anything tighter than about ±0.002" is ground after ageing rather than machined. 

Process Tolerance Surface Finish
CNC turning, standard ±0.0005" Up to 8 Ra
Precision turning ±0.0002" Up to 8 Ra, polishing available
CNC milling, 3- and 4-axis ±0.001" (excluding true-position callouts) 32 Ra side / 63 Ra face
5-axis milling ±0.001" linear · ±0.002–0.003" rotational · ±0.003" tilted-hole 32 Ra
INTEGREX / Hyper Quadrex mill-turn ±0.0005" 32 Ra
OD, surface and Blanchard grinding ±0.0005" to ±0.0002" Up to 8 Ra
Wire EDM ±0.0005" to ±0.0002" 16–32 Ra, fine to 8 Ra
EDM - Side of part

How We Machine Hastelloy & Monel

Turning runs on 28 CNC lathes at deliberately low surface speeds, with precision turning to ±0.0002" and Swiss platforms for small diameters. Cold drawn and stress-relieved bar gives markedly better machinability than annealed on Monel 400 it is the first thing we look at when quoting. 

Milling runs across 36 vertical machining centers, eight horizontals and five five-axis verticals, with rigid setups, high-pressure coolant and short tool paths throughout. 

EDM frequently makes the economic case on the Hastelloy grades. Five wire EDM machines and two RAM EDM machines cut features with no mechanical cutting force, which removes both the work-hardening mechanism and the tool-life problem. On slots, thin profiles and intricate geometry in C-276 or C-22, wire EDM is often faster and cheaper than milling despite the lower material removal rate. 

Age hardening of Monel K-500 runs in our own furnaces within the 2100°F range, with grinding to Ø16" × 60" OD and 32" × 20" × 18" surface capacity for post-ageing sizing. 

 What Makes Hastelloy and Monel Different

These alloys are chosen for what they survive in service, and the same chemistry that protects them is what makes them demanding to machine. 

The Hastelloy C grades are the hardest thing in the shop

C-276 and C-22 combine extreme corrosion resistance with the worst work hardening and gumminess in common industrial use. The rules are absolute: very low surface speed, heavy positive rake, razor-sharp tooling replaced on schedule rather than on failure, rigid setup, high-pressure coolant, and no dwelling under any circumstances. A tool that rubs instead of cutting creates a hardened skin that will destroy the next tool. Keep it moving and take a real cut. 

Monel 400 is a different proposition

Gummy, long chipping and work-hardening, but distinctly easier than the Hastelloys. Cold-drawn or cold-drawn-and-stress-relieved bar gives the best machinability by a clear margin. Chip control is the practical production issue chipbreaker geometry and adequate feed rather than light cuts. 

Monel K-500 galls

K-500 is age hardenable through aluminium and titanium additions, reaching HRC 27 to 35 aged, and it is notorious for galling and for severe work hardening. That galling resistance in service is exactly why it is chosen for marine shafting and non sparking tools, but in the cut it means sharp tools, real depths of cut and no rubbing. Buy annealed for machine-then-age, or aged for as-machined parts where the tolerance permits. 

There is no reliable published machinability percentage for C-22, C-276, B-2 or the Monels. The only published superalloy figure is Hastelloy X at 19 percent on the AISI scale, and the C grades are regarded as equal to or worse. The mill grouping system places Monel 400 in Group B and aged K-500 in Group D. We do not quote a percentage for these alloys because no primary source publishes one.

Finishing and Post-Processing

In-house at Steelcrest

  • Age hardening of Monel K-500 and stress relief within our 2100°F furnace range
  • Saw cutting and bar preparation
  • Laser etching for lot traceability marking
  • Deburring, CMM and FARO Arm inspection

Managed through qualified partners

  • Descaling and pickling
  • Electropolishing for chemical-process and pharmaceutical service
  • Passivation where a customer specification calls for it


NOTE*:  As with all nickel alloys, ASTM A967 and AMS 2700 are stainless specifications and do not cover Hastelloy or Monel. Specify the vendor process or your own customer specification rather than a generic passivation callout. These alloys are themselves the corrosion solution plating is rarely appropriate

Industries We Machine Hastelloy and Monel For 

Steelcrest Precision machines Hastelloy C-22, C-276 and B-2, and Monel 400 and K-500, for aerospace and defense and medical and pharmaceutical applications, along with chemical processing, marine, and oil and gas customers who come to us directly. 

We also machine these alloys for chemical processing, marine, oil and gas and pollution-control customers who come to us directly. Those markets do not have a dedicated page on this site, but severe corrosion work is a routine part of what runs through the shop, and Monel in particular is a long-standing marine material for us. 

Talk To Us About Your Hastelloy & Monel Parts. 

Send the drawing and the quantity. We will come back with a real number, a real lead time, and if there is a better material or condition for what the part has to do we will tell you that too. 

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Frequently Asked Questions

Is Hastelloy harder to machine than Inconel?

Yes. The Hastelloy C grades represent the worst combination of work hardening and gumminess in common industrial use meaningfully harder than Inconel 718, which is itself among the most difficult aerospace alloys. Expect lower speeds, shorter tool life and more EDM in the process plan. 

Would EDM be cheaper than milling on my Hastelloy part?

Often, yes. On slots, thin profiles, blind cavities and intricate geometry, wire or RAM EDM removes cutting force from the equation entirely, which eliminates both the work-hardening mechanism and the tool-life cost. Send the drawing and we will tell you which route is cheaper for your specific geometry. 

Which Hastelloy grade should I specify?

C-276 is the general-purpose severe-corrosion choice. C-22 offers broader resistance across both oxidising and reducing conditions. B-2 is specifically for reducing acids, principally hydrochloric, and is not appropriate for oxidising service. If you are unsure, the environment determines it tell us the service conditions. 

Do you age harden Monel K-500 in-house?

Yes, within our 2100°F furnace range, with OD and surface grinding available afterwards for parts requiring tolerances tighter than about ±0.002" in the aged condition. 

Can you passivate Hastelloy and Monel?

We manage it through qualified partners where a customer specification calls for it. Be aware that ASTM A967 and AMS 2700 are stainless specifications and do not cover these alloys, so the drawing needs to name a vendor process or your own specification. 

Do you supply material certifications?

Yes — material certifications and a certificate of conformance ship with the parts, and mill certificates can be held on file against your part number for repeat orders.